1. Field of the Invention
The present invention relates to an impact detector to detect impact to an article and a packaging container including the impact detector.
2. Discussion of the Background Arts
In the course of transport, it sometimes happens that fragile packaged articles such as precision equipment fall or are dropped due to inappropriate handling, accidents, or the like. The impact of the fall or drop can damage the articles. Articles can be prevented from being damaged by impact of a predetermined magnitude or smaller by taking damage prevention measures on the basis of pre-assessment of packaged articles.
For example, impact detectors may be used that include a weight having a smooth surface reflecting incident light and a beam supporting the weight. When impact of the fall or drop is detected, the weight tilts, enabling users to recognize that the impact detector has detected an impact.
FIGS. 1A through 1E illustrate another configuration of impact detectors. FIG. 1A is an exploded perspective view illustrating an impact detector 100Z, FIG. 1B illustrates an appearance of the impact detector 100Z, FIG. 1C illustrates an initial state of the impact detector 100Z, FIG. 1D illustrates a weight 6 moving in the impact detector 100Z due to impact thereto, and FIG. 1E illustrates an impact detections state of the impact detector 100Z.
As illustrated in FIG. 1A, the impact detector 100Z includes a front case 1, a rear case 2, a leaf spring 3, a leaf spring fixing portion 4, guide plates 5, the weight 6, and window holes 7. The impact detector 100Z can detect impact from below to a target article to which the impact detector 100Z at the position shown in FIG. 1B is attached, that is, the impact detector 100Z can detect that the article has been dropped. More specifically, as shown in FIG. 1C, at the initial state when the target article is not subjected to impact, the weight 6 is at an initial position, sandwiched by the leaf spring 3 and a wall 8 of the front case 1 and thus held in a center area of the impact detector 100Z. When the impact detector 100Z receives an impact from below, the weight 6 moves downward, overstrides a lower portion of the leaf spring 3, and then reaches an impact detection position at a bottom of the impact detector 100Z as shown in FIGS. 1D and 1E. The weight 6 may be colored to facilitate visual recognition of the weight 6 through the lower window hole 7.
However, the impact detector 100Z illustrated in FIGS. 1A through 1E has several drawbacks. For example, the impact detection accuracy of the impact detector 100Z tends to vary. That is, although the detection level is selectable among multiple different levels by changing the mass of the weight while an identical leaf spring is used for the respective detection levels in this type of impact detectors, actual detection performance can differ from the set detection level significantly, and thus the impact detector has relatively low detection accuracy.
One cause of the difference between the actual detection performance and the set detection level is the bending of an attachment base of the leaf springs 3, which is described in further detail below with reference to FIGS. 2A and 2B.
Referring to FIG. 2A, a gap greater than the thickness of the leaf springs 3 is formed between the front case 1 and the rear case 2 to insert therein the leaf springs 3, and a member for fixing the leaf springs 3 to the front case 1 is absent in a region indicated by reference numeral 9 shown in FIG. 2B. The bending of the base of the leaf springs 3 is caused by the impact received by the entire lower leaf spring 3. As a result, the resilient force of the leaf spring 3 is reduced, degrading the impact detection accuracy.